1. Field of the Invention
The present invention relates to a cathode ray tube (xe2x80x9cCRTxe2x80x9d) and, more particularly to a filming solution and method for forming a filming layer on a CRT.
2. Description of the Prior Art
Generally, a phosphor screen of a CRT converts electron beam energy radiated from an electron gun into optical energy to realize an image is by exciting a phosphor. The phosphor screen is formed through a black matrix forming process and an RGB pattern forming process.
The phosphor screen is covered by an aluminum layer to increase brightness and prevent the phosphor screen from experiencing a potential drop and being burned. The aluminum layer is formed by evaporation and diffusing aluminum material on the phosphor screen under the vacuum condition.
However, since a plurality of phosphor holes are formed on red, green, blue phosphors of the phosphor screen, when evaporating the aluminum material on the phosphor screen, the aluminum material is filled into the phosphor holes, deteriorating a mirror effect of the aluminum layer.
To solve the above problem, coating material is deposited on the phosphor screen such that the coating material is filled in the phosphor holes. That is after the phosphor screen is formed on an inner surface of a panel, a film solution is deposited on the phosphor screen to flatten the surface of the phosphor screen. After that, the aluminum layer is deposited on the filming solution, thereby reducing the uneven surface rate of the aluminum layer. As a result, the reflecting effect is enhanced to improve the brightness of a CRT display.
Such a coating layer is preferably an organic film, which does not affect the phosphor screen and the radiation of the electron beams from the electron gun. A process for forming the organic film on the phosphor screen is called a filming process.
In addition, after the aluminum layer is deposited on the organic film, a baking process should be performed to completely remove unnecessary organic material. That is, the phosphor screen on which the aluminum layer is deposited is heated at a temperature of about 350-450xc2x0 C.
There are two conventional filming technologies: one uses aqueous acryl emulsion and the other uses oil lacquer.
In the technology using the aqueous acryl emulsion, polyvinyl alcohol, acryl emulsion, glycerin, ammonium hydroxide (NH4OH), and hydrogen peroxide are added. Therefore, a baking process for removing unnecessary organic material of the phosphor screen and filming layer should be conducted at a temperature of 400-450xc2x0 C., after which a flit sealing process for combining a panel and a funnel should be conducted at a temperature of 400-450xc2x0 C.
However, the baking process is time-consuming. If the baking process is not conducted, the unnecessary organic material generates an organic gas during the flit sealing process, making it difficult to effectively combine the panel and the funnel to each other.
In the case of technology using the oil lacquer, although the baking process is not required since the amount of the organic material is small. However since the oil lacquer is so flammable, an additional safety system is required.
Therefore, the present invention has been made in an effort to solve the above-described problems of the prior art.
It is a first objective of the present invention to provide a filming method of a CRT, which can form a filming layer on a phosphor screen using an acryl emulsion without additional baking process.
It is another objective of the present invention to provide a filming solution containing an acryl emulsion which can be formed on a phosphor screen as a filming layer.
To achieve the first objective, the present invention provides a method for forming a filming layer of a cathode ray tube, comprising the steps of depositing a filming solution comprising more than 70 wt % of butyl methacrylate on a phosphor screen, and spraying ammonium oxalate solution on the deposited filming solution.
The method may further comprise the step of causing the film to be undergone a baking process. Preferably, the baking process is conducted simultaneously with a flit sealing process for combining a panel and a funnel with each other.
To achieve the second objective, the present invention provides a filming solution comprising a copolymerized emulsion having more than 70 wt % of butyl methacrylate and at least one monomer, and more than one species of additive.
Preferably, the monomer is selected from the group consisting of acrylic acid derivative, methacrylic acid derivative, styrene, acrylamide and acrylonitrile.
Preferably, the acrylic acid derivative is selected from the group consisting of acrylic acid methyl acrylate, ethyl acrylate, and benzyl acrylate. In addition, the methacrylic acid derivative is selected from the group consisting of methacrylic acid, methyl methacrylate, ethyl methacrylate, hydroxyethyl methacrylate, isobonyl methacrylate, benzyl methacrylate, and phenoxy methacrylate.
Preferably, an amount of the emulsion in the filming solution is about 4-40 wt % in a solid state.
The additive is selected from the group consisting of polyvinyl alcohol, hydrogen peroxide, surface active agent and antifoaming agent.
The filming solution may further comprise a viscosity enhancing material.